# Create a target tracking scaling policy for Application Auto Scaling using the AWS CLI
This example uses AWS CLI commands to create a target racking policy for an Amazon EC2 Spot Fleet. For a different scalable target, specify its namespace in `--service-namespace`, its scalable dimension in `--scalable-dimension`, and its resource ID in `--resource-id`.
When using the AWS CLI, remember that your commands run in the AWS Region configured for your profile. If you want to run the commands in a different Region, either change the default Region for your profile, or use the `--region` parameter with the command.
**Topics**
+ [Step 1: Register a scalable target](#target-tracking-register-scalable-target)
+ [Step 2: Create a target tracking scaling policy](#create-target-tracking-policy)
+ [Step 3: Describe target tracking scaling policies](#describe-target-tracking-policy)
## Step 1: Register a scalable target
If you haven't already done so, register the scalable target. Use the [register-scalable-target](https://docs.aws.amazon.com/cli/latest/reference/application-autoscaling/register-scalable-target.html) command to register a specific resource in the target service as a scalable target. The following example registers a Spot Fleet request with Application Auto Scaling. Application Auto Scaling can scale the number of instances in the Spot Fleet at a minimum of 2 instances and a maximum of 10. Replace each *user input placeholder* with your own information.
**Linux, macOS, or Unix**
```
aws application-autoscaling register-scalable-target --service-namespace ec2 \
--scalable-dimension ec2:spot-fleet-request:TargetCapacity \
--resource-id spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE \
--min-capacity 2 --max-capacity 10
```
**Windows**
```
aws application-autoscaling register-scalable-target --service-namespace ec2 ^
--scalable-dimension ec2:spot-fleet-request:TargetCapacity ^
--resource-id spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE ^
--min-capacity 2 --max-capacity 10
```
**Output**
If successful, this command returns the ARN of the scalable target. The following is example output.
```
{
"ScalableTargetARN": "arn:aws:application-autoscaling:region:account-id:scalable-target/1234abcd56ab78cd901ef1234567890ab123"
}
```
## Step 2: Create a target tracking scaling policy
To create a target tracking scaling policy, you can use the following examples to help you get started.
**To create a target tracking scaling policy**
1. Use the following `cat` command to store a target value for your scaling policy and a predefined metric specification in a JSON file named `config.json` in your home directory. The following is an example target tracking configuration that keeps the average CPU utilization at 50 percent.
```
$ cat ~/config.json
{
"TargetValue": 50.0,
"PredefinedMetricSpecification":
{
"PredefinedMetricType": "EC2SpotFleetRequestAverageCPUUtilization"
}
}
```
For more information, see [PredefinedMetricSpecification](https://docs.aws.amazon.com/autoscaling/application/APIReference/API_PredefinedMetricSpecification.html) in the *Application Auto Scaling API Reference*.
Alternatively, you can use a custom metric for scaling by creating a customized metric specification and adding values for each parameter from CloudWatch. The following is an example target tracking configuration that keeps the average utilization of the specified metric at 100.
```
$ cat ~/config.json
{
"TargetValue": 100.0,
"CustomizedMetricSpecification":{
"MetricName": "MyUtilizationMetric",
"Namespace": "MyNamespace",
"Dimensions": [
{
"Name": "MyOptionalMetricDimensionName",
"Value": "MyOptionalMetricDimensionValue"
}
],
"Statistic": "Average",
"Unit": "Percent"
}
}
```
For more information, see [CustomizedMetricSpecification](https://docs.aws.amazon.com/autoscaling/application/APIReference/API_CustomizedMetricSpecification.html) in the *Application Auto Scaling API Reference*.
1. Use the following [put-scaling-policy](https://docs.aws.amazon.com/cli/latest/reference/application-autoscaling/put-scaling-policy.html) command, along with the `config.json` file you created, to create a scaling policy named `cpu50-target-tracking-scaling-policy`.
**Linux, macOS, or Unix**
```
aws application-autoscaling put-scaling-policy --service-namespace ec2 \
--scalable-dimension ec2:spot-fleet-request:TargetCapacity \
--resource-id spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE \
--policy-name cpu50-target-tracking-scaling-policy --policy-type TargetTrackingScaling \
--target-tracking-scaling-policy-configuration file://config.json
```
**Windows**
```
aws application-autoscaling put-scaling-policy --service-namespace ec2 ^
--scalable-dimension ec2:spot-fleet-request:TargetCapacity ^
--resource-id spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE ^
--policy-name cpu50-target-tracking-scaling-policy --policy-type TargetTrackingScaling ^
--target-tracking-scaling-policy-configuration file://config.json
```
**Output**
If successful, this command returns the ARNs and names of the two CloudWatch alarms created on your behalf. The following is example output.
```
{
"PolicyARN": "arn:aws:autoscaling:region:account-id:scalingPolicy:policy-id:resource/ec2/spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE:policyName/cpu50-target-tracking-scaling-policy",
"Alarms": [
{
"AlarmARN": "arn:aws:cloudwatch:region:account-id:alarm:TargetTracking-spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE-AlarmHigh-d4f0770c-b46e-434a-a60f-3b36d653feca",
"AlarmName": "TargetTracking-spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE-AlarmHigh-d4f0770c-b46e-434a-a60f-3b36d653feca"
},
{
"AlarmARN": "arn:aws:cloudwatch:region:account-id:alarm:TargetTracking-spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE-AlarmLow-1b437334-d19b-4a63-a812-6c67aaf2910d",
"AlarmName": "TargetTracking-spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE-AlarmLow-1b437334-d19b-4a63-a812-6c67aaf2910d"
}
]
}
```
## Step 3: Describe target tracking scaling policies
You can describe all scaling policies for the specified service namespace using the following [describe-scaling-policies](https://docs.aws.amazon.com/cli/latest/reference/application-autoscaling/describe-scaling-policies.html) command.
```
aws application-autoscaling describe-scaling-policies --service-namespace ec2
```
You can filter the results to just the target tracking scaling policies using the `--query` parameter. For more information about the syntax for `query`, see [Controlling command output from the AWS CLI](https://docs.aws.amazon.com/cli/latest/userguide/cli-usage-output.html) in the *AWS Command Line Interface User Guide*.
**Linux, macOS, or Unix**
```
aws application-autoscaling describe-scaling-policies --service-namespace ec2 \
--query 'ScalingPolicies[?PolicyType==`TargetTrackingScaling`]'
```
**Windows**
```
aws application-autoscaling describe-scaling-policies --service-namespace ec2 ^
--query "ScalingPolicies[?PolicyType==`TargetTrackingScaling`]"
```
**Output**
The following is example output.
```
[
{
"PolicyARN": "PolicyARN",
"TargetTrackingScalingPolicyConfiguration": {
"PredefinedMetricSpecification": {
"PredefinedMetricType": "EC2SpotFleetRequestAverageCPUUtilization"
},
"TargetValue": 50.0
},
"PolicyName": "cpu50-target-tracking-scaling-policy",
"ScalableDimension": "ec2:spot-fleet-request:TargetCapacity",
"ServiceNamespace": "ec2",
"PolicyType": "TargetTrackingScaling",
"ResourceId": "spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE",
"Alarms": [
{
"AlarmARN": "arn:aws:cloudwatch:region:account-id:alarm:TargetTracking-spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE-AlarmHigh-d4f0770c-b46e-434a-a60f-3b36d653feca",
"AlarmName": "TargetTracking-spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE-AlarmHigh-d4f0770c-b46e-434a-a60f-3b36d653feca"
},
{
"AlarmARN": "arn:aws:cloudwatch:region:account-id:alarm:TargetTracking-spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE-AlarmLow-1b437334-d19b-4a63-a812-6c67aaf2910d",
"AlarmName": "TargetTracking-spot-fleet-request/sfr-73fbd2ce-aa30-494c-8788-1cee4EXAMPLE-AlarmLow-1b437334-d19b-4a63-a812-6c67aaf2910d"
}
],
"CreationTime": 1515021724.807
}
]
```